https://sourceware.org/bugzilla/show_bug.cgi?id=31318
Bug ID: 31318
Summary: RISC-V 32-bit relocations truncated silently
Product: binutils
Version: 2.43 (HEAD)
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: Joseph.Faulls at imgtec dot com
Target Milestone: ---
Hi,
It seems handling relocations of type R_RISCV_32 does not error if there is a
truncation. This does not seem right to me.
This was discovered when placing a program at very high addresses (> max_int),
and the relocations emitted by the (clang) compiler in a jump table (from an
optimised switch-case) in the data section were truncated. This resulted in a
run-time failure. Supplying -mcmodel=medany solves this.
Reproducing test case:
test.s:
.macro DATA symbol
.word \symbol
.endm
DATA abs
$ as test.s -march=rv64i -mabi=lp64 -defsym __abs__=1 -o test.o
$ ld -melf64lriscv -Ttext 0x8000 --defsym _start=0x0 --defsym abs=0xc00005000
--defsym abs_local=0x200 test.o -o test.elf
$ objdump -dr test.elf
Disassembly of section .text:
0000000000008000 <__DATA_BEGIN__-0x1004>:
8000: 00005000 .word 0x00005000
Should this not error as we're truncating the address?
I've spent a while debugging, but this is the best fix I can come up with:
diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 8b27e3b8d6a..91a552a3dc2 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -1866,6 +1866,9 @@ perform_relocation (const reloc_howto_type *howto,
case R_RISCV_32:
case R_RISCV_64:
+ if (value & ~howto->dst_mask)
+ return bfd_reloc_overflow;
+ break;
case R_RISCV_ADD8:
case R_RISCV_ADD16:
case R_RISCV_ADD32:
However, I don't really know if this is a reasonable fix. What do people think?
Thanks,
Joe
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